Abstract
This paper reports findings from an investigation into the effect of flow rate and organic inhibitor on the material performance, film thickness and hardness of protective scales formed on X65 carbon steel surface in a rotating cylinder electrode (RCE) system. The experiments were conducted at a temperature of 70 °C, pH of 5.9 and 4.5 g/cm.s2 wall shear stress (τw) using both uninhibited and inhibited Forties brine with 25 ppm of inhibitor saturated with carbon dioxide (CO2) containing 0.1% HST60 PSA silica sand, which can be described as semi-spherical with sharp edges. Weight gain/loss was measured for: as-received X65 specimens and specimens before and after removing corrosion scales in both uninhibited and inhibited systems. In addition, the hardness of the surface specimens and scales was measured using a nano-indenter. This was supported by post-test analysis of samples using scanning electron microscopy (SEM), focus ion beam SEM (FIBSEM), energy dispersive X-ray spectroscopy (EDX) to assess the nature, the thickness, the elemental composition and the possible salts forming these protective films. It was found that the weight loss of as-received surfaces was reduced by more than 43% when 25 ppm of inhibitor was introduced. Nevertheless, inhibitor was found not to be effective in reducing weight loss of pre-scaled surfaces.
